Growth of aligned hexagonal ZnO nanorods on FTO substrate for dye-sensitized solar cells (DSSCs) application

This article reports a facile growth of well-crystalline aligned hexagonal ZnO nanorods on fluorine-doped tin-oxide (FTO) substrate via non-catalytic thermal evaporation process. The morphological investigations done by field-emission scanning electron microscope (FESEM) and transmission electron microscopy (TEM) reveal that the grown products are aligned hexagonal ZnO nanorods which are grown in a very high density over the whole substrate surface. The detailed structural properties observed by high-resolution TEM equipped with selected area electron diffraction (SAED) and X-ray diffraction (XRD) pattern confirmed that the synthesized nanorods are well-crystalline possessing wurtzite hexagonal phase and preferentially grown along the c-axis direction. A sharp and strong UV emission at 381 nm in room-temperature photoluminescence (PL) spectrum showed that the as-grown ZnO nanorods possess excellent optical properties. The as-grown nanorods were used as photo-anode for the fabrication of dye-sensitized solar cells (DSSCs) which exhibits an overall light-to-electricity conversion efficiency (ECE) of 0.7% with V(oc) of 0.571 V, J(sc) of 2.02 mA/cm2 and FF of 0.58.     

Two-step growth of hexagonal-shaped ZnO nanowires and nanorods and their properties

Single-crystalline with perfect hexagonal-shaped ZnO nanowires and nanorods, possessing the Zn-terminated (0001) facets bounded with the six-crystallographic equivalent [0110] surfaces, have been grown on Au-coated silicon substrate via thermal evaporation method using the metallic zinc powder in presence of oxygen. The detailed structural analyses reveal that the obtained nanostructures are single-crystalline with the wurtzite hexagonal phase and are preferentially oriented in the c-axis, [0001] direction. Raman spectra exhibit a sharp and strong optical phonon E2 mode at 437 cm(-1) further confirms the good crystal quality with wurtzite hexagonal crystal structure for the deposited products. The room-temperature photoluminescence (PL) spectra, for both the structures, showed a sharp and strong UV emission with a suppressed green emission, indicating the good optical properties for the as-grown nanostructures.     

Growth and properties of ultra-violet emitting aligned zinc oxide nanocones with hexagonal caps

Ultraviolet-emitting, single-crystalline aligned zinc oxide (ZnO) nanocones with hexagonal caps were grown on silicon substrate via simple non-catalytic thermal evaporation process. High-purity metallic zinc powder and oxygen were used as source materials for zinc and oxygen, respectively. The detailed structural characterizations confirmed that the formed products are single-crystalline, possess a wurtzite hexagonal phase and grown along the c-axis direction. Raman-active optical-phonon E2(high) mode at 437 cm(-1) with sharp and strong UV emission at 385 nm in room-temperature photoluminescence (PL) spectrum demonstrated that the as-grown ZnO nanocones with hexagonal caps possess good-crystal quality with the excellent optical properties. Finally, a plausible growth mechanism for the formation of as-grown ZnO nanocones with hexagonal caps was also proposed.     

Effect of Fe doping concentration on optical and magnetic properties of ZnO nanorods

Herein, a facile low temperature, aqueous solution-based chemical method has been demonstrated for large-scale fabrication of Fe doped ZnO nanorods (ZnO:Fe) with a series percentage of Fe dopant. Interestingly, the SEM results reveal a uniform well dispersed synthesis of ZnO:Fe nanorods throughout the substrate. The x-ray diffraction result suggests that Fe substitutes Zn in the ZnO matrix and rules out the formation of any secondary phase. Selected area electron diffraction investigation verifies the single crystal, hexagonal wurtzite structure of the ZnO:Fe nanorods. Energy dispersive spectroscopy data confirm Fe doping of the ZnO nanorods with a concentration ranging from 0.9 to 2.2 at.%. The photoluminescence spectrum reveals a continuous suppression of defect related broad-band emission (I(D)/I(UV) = 1-0.11) by increasing the concentration of the dopant ion, which produces the quenching of surface defects present in the nanostructures. An enhancement in ferromagnetism (M = 0.15 × 10?2-0.24 × 10?1 emu g?1 at 2000 Oe) is found in doped ZnO nanorods.     

Temperature dependant characteristics of zinc oxide nanorods based heterojunction diode

Temperature-dependant characteristics of heterojunction diode made by n-ZnO nanorods grown on p-silicon substrates has been characterized and demonstrated in this paper. ZnO nanorods were grown onto the silicon substrate via simple thermal evaporation process by using metallic zinc powder in the presence of oxygen at approximately 550 degrees C without the use of any metal catalysts or additives. The as-grown ZnO nanorods were characterized in terms of their structural and optical properties. The detailed structural studies by XRD, TEM, HRTEM and SAED revealed that the grown nanorods are well-crystalline with the wurtzite hexagonal phase and preferentially grown along the [0001] direction. The as-grown n-ZnO nanorods grown on p-Si substrate were used to fabricate p-n heterojunction diode. The fabricated p-n junction diode attained almost similar turn-on voltage of approximately 0.6 V. The values of turn-on voltage and least current are same with the variations of temperature (i.e., 27 degrees C, 70 degrees C and 130 degrees C).     

Synthesis of novel zinc oxide microphone-like microstructures

Novel microphone-like ZnO microstructures were grown at a very high density via a simple thermal evaporation process using commercially available ZnO powder in ambient air at ∼ 1050 ± 20 °C in 1 h. The unique as-grown microstructures were characterized in detail in terms of their structural and optical properties. The structural properties of the synthesized products confirmed that they were wurtzite hexagonal phase for the as-grown products. Raman-scattering spectra exhibited a strong and dominated Raman-active E₂ (high) mode at 441 cm^− 1, confirming the wurtzite hexagonal phase for the as-grown microphone-like ZnO morphologies. The cathodoluminescence (CL) spectrum shows a suppressed near band edge emission at ∼ 380 nm and strong green emission at ∼ 500 nm.     

Defect induced room temperature ferromagnetism in well-aligned ZnO nanorods grown on Si (100) substrate

In this work, we report the fabrication of high quality single-crystalline ZnO nanorod arrays which were grown on the silicon (Si) substrate using a microwave assisted solution method. The as grown nanorods were characterized using X-ray diffraction (XRD), field emission scanning electron microscopy (FE-SEM), photo-luminescence (PL) and magnetization measurements. The XRD results indicated that the ZnO nanorods are well oriented with the c-axis perpendicular to the substrate and have single phase nature with the wurtzite structure. FE-SEM results showed that the length and diameter of the well aligned rods is about ~ 1 μm and ~ 100 nm respectively, having aspect ratio of 20-30. Room-temperature PL spectrum of the as-grown ZnO nanorods reveals a near-band-edge (NBE) emission peak and defect induced green light emission. The green light emission band at ~ 583 nm might be attributed to surface oxygen vacancies or defects. Magnetization measurements show that the ZnO nanorods exhibit room temperature ferromagnetism which may result due to the presence of defects in the ZnO nanorods.     

Structural and optical properties of ZnO nanostructures grown on silicon substrate by thermal evaporation process

Two types of one-dimensional ZnO nanostructures have been synthesized on silicon substrate by the thermal evaporation of metallic zinc powder in the presence of oxygen without the use of any catalyst or additives. Detailed structural analysis revealed that the formed ZnO nanostructures are single crystalline with wurtzite hexagonal phase and grow along the [0001] direction in preference. Presence of a sharp and strong, optical phonon Raman-active E₂ (high) mode and suppressed E₁ (LO) mode in the Raman spectra, in both the cases, confirmed the good crystallinity with the wurtzite hexagonal phase for the as-grown products. A sharp and dominant near band edge emission with a suppressed green emission is observed from the as-synthesized nanostructures which affirmed the good optical properties with very less structural defects for the grown nanostructures.     

Direct synthesis of ZnO nanowire arrays on Zn foil by a simple thermal evaporation process

ZnO nanowire arrays were synthesized on zinc foil by a simple thermal evaporation process at relatively low temperature. Morphology and size controlled synthesis of the ZnO nanostructures was achieved by variation of the synthesis temperature, reaction time and the surface roughness of the substrate. A gas-solid and self-catalytic liquid-solid mechanism is proposed for the growth of nanowires at different temperatures. High-resolution transmission electron microscopy (HRTEM) showed that the as-grown nanowires were of single crystal hexagonal wurtzite structure, growing along the [101] direction. Photoluminescence exhibited strong UV emission at ～382?nm and a broad green emission at ～513?nm with 325?nm excitation. Raman spectroscopy revealed a phonon confinement effect when compared with results from bulk ZnO. The nanowire arrays also exhibited a field emission property.     

Epitaxial growth of ZnO nanorods on electrospun ZnO nanofibers by hydrothermal method

In this paper, we report a new ZnO nanofibers-nanorods structure which was successfully prepared by the electrospun ZnO nanofibers as seed to guide hydrothermal epitaxial growth of the ZnO nanorods. The structure was characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and photoluminescence (PL). The XRD results indicate that ZnO nanofibers obtained at 600° have high crystallinity with a typical hexagonal wurtzite structure. Furthermore compared with the strongest diffraction of ZnO nanofibers in (101) plane, the diffraction from (002) plane of ZnO nanofibers-nanorods becomes the strongest. The SEM shows that the diameters of epitaxial-grown ZnO nanorods on ZnO nanofibers were approximately 100–200?nm. The PL spectrum shows that the ZnO nanofibers-nanorods have a broad green-yellow emission around 537?nm, in contrast to that of ZnO nanofibers, the peak had obvious redshift about 24?nm and the luminous intensity weakened.     

ZnO纳米棒Al掺杂和A1,N共掺杂的制备技术与光致发光性能

采用水热法首先合成了Al掺杂ZnO(AZO)纳米棒,在此基础上通过550℃的氨气氛中退火制备了Al,N共掺杂ZnO(ANZ())纳米棒.运用X射线衍射(XRD),场发射扫描电镜(FESEM),透射电子显微镜(TEM),X射线能谱(EDS)和光致发光(PL)对样品进行了表征与分析.结果表明,制备的AZO和ANZ()纳米棒...     

Low temperature solution synthesis and characterization of ZnO nano-flowers

Synthesis of flower-shaped ZnO nanostructures composed of hexagonal ZnO nanorods was achieved by the solution process using zinc acetate dihydrate and sodium hydroxide at very low temperature of 90 °C in 30 min. The individual nanorods are of hexagonal shape with sharp tip, and base diameter of about 300-350 nm. Detailed structural characterizations demonstrate that the synthesized products are single crystalline with the wurtzite hexagonal phase, grown along the [0 0 0 1] direction. The IR spectrum shows the standard peak of zinc oxide at 523 cm⁻¹. Raman scattering exhibits a sharp and strong E₂ mode at 437 cm⁻¹ which further confirms the good crystallinity and wurtzite hexagonal phase of the grown nanostructures. The photoelectron spectroscopic measurement shows the presence of Zn, O, C, zinc acetate and Na. The binding energy ca. 1021.2 eV (Zn 2p_3/2) and 1044.3 eV (Zn 2p_1/2), are found very close to the standard bulk ZnO binding energy values. The O 1s peak is found centered at 531.4 eV with a shoulder at 529.8 eV. Room-temperature photoluminescence (PL) demonstrate a strong and dominated peak at 381 nm with a suppressed and broad green emission at 515 nm, suggests that the flower-shaped ZnO nanostructures have good optical properties with very less structural defects.     

Novel synthesis of aligned Zinc oxide nanorods on a glass substrate by sonicated sol-gel immersion

For the first time, aligned ZnO nanorod structured thin films have been synthesized on a glass substrate, which had been coated with an Al-doped ZnO thin film, using the sonicated sol-gel immersion method. These nanorods were found to have an average diameter of 100 nm and an average length of 500 nm, with hexagonal wurtzite phase grew preferentially along the c-axis direction. A sharp ultra-violet (UV) emission centred at 383 nm corresponding to the free exciton recombination was observed in a room temperature photoluminescence (PL) spectrum. The prepared ZnO nanorod structured thin film is transparent in the visible region with an average transmittance of 78% in the 400-800 nm wavelength range and high absorbance properties in the UV region (< 400 nm). The results indicate that the prepared ZnO nanorods are suitable for ultra-violet photoconductive sensor applications.     

High-yield chemical synthesis of hexagonal ZnO nanoparticles and nanorods with excellent optical properties

Large yield and low temperature growth of nanostructures are key requirements for fulfilling the demand of large scale applications of nanomaterials. Here, we report a highly efficient chemical method to synthesize high quality hexagonal ZnO nanoparticle and nanorods utilizing the low temperature oxidation of metallic zinc powder in the presence of an appropriate catalyst. This one-step method has advantages such as low temperature (90 degrees C) and atmospheric pressure synthesis and a high yield (> 90%). Microstructure and optical properties of the as-synthesized ZnO nanoparticles are found to be identical or better than those of the commercial ZnO nanopower (Sigma-Aldrich). In particular, in comparison to the commercial nanopowder the as-grown ZnO nanorods and nanoparticles exhibit stronger UV absorption at 376 nm and intense UV photoluminescence emission at -382 nm, with negligible defect emission band. This method is suitable for large-scale production of nanosized ZnO and could be extended for the synthesis of other metal oxides.     

ZnO纳米棒阵列膜的制备及其光电化学性能研究

采用化学溶液沉积法,在ZnO纳米颗粒膜修饰的FTO导电玻璃基底上,制备了ZnO纳米棒阵列。用X射线衍射仪（XRD）、场发射扫描电子显微镜（FESEM）、透射电子显微镜（TEM）对样品进行表征。研究结果表明所制备的ZnO纳米棒为六方纤锌矿相单晶结构,沿c轴择优取向生长,平均直径约为40nm,长度约为900nm;ZnO纳米棒阵列生长致密,取向性较一致。以曙红Y敏化的ZnO纳米棒阵列膜为光阳极制作了染料敏化太阳能电池原型器件,在光照强度为100mW/cm2下,其开路电压为0.418V,短路电流为0.889mA/cm2,总的光电转换效率为0.133%。     

ZnO单晶堆垒纳米棒的制备与表征

在Au点阵模板上磁控溅射ZnO薄膜,然后在O2气氛下1000℃退火制备了ZnO单晶堆垒纳米棒。采用扫描电子显微镜(SEM)、高分辨透射电子显微镜(HRTEM)、X射线衍射(XRD)和傅立叶变换红外(FTIR)光谱对样品进行分析。结果表明,ZnO纳米棒是由诸多单晶堆垒而成,每个单晶均为六方纤锌矿结构,纳米棒直径在100nm左右。初步探讨了ZnO单晶堆垒纳米棒可能的生长机理。     

Growth of zinc oxide nanorods, tetrapods, and nanobelts without catalyst

Zinc oxide (ZnO) nanostructures with various morphologies have been synthesized without catalyst in a one-step simple redox process. The results show that ZnO nanorods, nanobelts, and tetrapods with hexagonal needled arms could be synthesized via thermal treatment of a mixture of zinc oxide and charcoal powder in a muffle furnace at 1000-1200 degrees C for 240 min. XRD analyses showed that polycrystalline ZnO phase with wurtzite crystal structure was formed. At a relatively low temperature, 1000 degrees C, the ZnO structure was found to be a bundle of denser nanorods. By increasing the reaction temperature to 1100 degrees C, tetrapod-like structures of needle-like arms with pyramidal tips were formed. With the increase of temperature up to 1200 degrees C, the morphology of ZnO nanostructures changed from nanorods and tetrapods to coalescence grains. Reaction temperature was found to be the most important experimental parameter that played an important role in controlling the mode, mechanism of growth, and formation of different ZnO morphologies.     

Effect of ZnO seed layer on the catalytic growth of vertically aligned ZnO nanorod arrays

We have grown vertically aligned ZnO nanorods and multipods by a seeded layer assisted vapor–liquid–solid (VLS) growth process using a muffle furnace. The effect of seed layer, substrate temperature and substrate material has been studied systematically for the growth of high quality aligned nanorods. The structural analysis on the aligned nanorods shows c-axis oriented aligned growth by homoepitaxy. High crystallinity and highly aligned ZnO nanorods are obtained for growth temperature of 850–900 °C. Depending on the thickness of the ZnO seed layer and local temperature on the substrate, some region of a substrate show ZnO tetrapod, hexapods and multipods, in addition to the vertically aligned nanorods. Raman scattering studies on the aligned nanorods show distinct mode at ∼438 cm⁻¹, confirming the hexagonal wurtzite phase of the nanorods. Room temperature photoluminescence studies show strong near band edge emission at ∼378 nm for aligned nanorods, while the non-aligned nanorods show only defect-emission band at ∼500 nm. ZnO nanorods grown without the seed layer were found to be non-aligned and are of much inferior quality. Possible growth mechanism for the seeded layer grown aligned nanorods is discussed.     

可见光诱导TiO2光催化及其机理研究进展

简述了二氧化钛的光催化机理。针对其禁带宽度较大,只能被小于387nm的紫外光所激发的缺点,综述了近年来国内外针对纳米TiO2可见光催化的改性方法和改性机理研究进展,包括离子掺杂、半导体复合、表面光敏化等方法。最后展望了提高纳米TiO2可见光光催化活性研究的前景。     

氨化Si基Ga2O3/Ti制备GaN纳米线

采用磁控溅射技术先在硅衬底上制备Ga2O3/Ti薄膜,然后在950℃时于流动的氨气中进行氨化反应制备GaN薄膜.X射线衍射(XRD)、傅立叶红外吸收光谱(FTIR)、选区电子衍射(SAED)和高分辨透射电子显微镜(HRTEM)的结果表明采用此方法得到了六方纤锌矿结构的GaN单晶纳米线.通过扫描电镜(SEM)观察发现纳米线的形貌,纳米棒的尺寸在50～150nm之间.